Is there any scientific evidence that lack of physical affection has adverse effects in human adults?

Question

There is an often-cited quote by Virginia Satir, saying

“We need 4 hugs a day for survival.
We need 8 hugs a day for maintenance.
We need 12 hugs a day for growth.”

This has been cited a lot, but I could not find a source for said quote. Furthermore, I tried to find scientific evidence that hugs or other signs of physical affection are required for "survival".

Traina, C. (2005). Touch on Trial: Power and the Right to Physical Affection. Journal of the Society of Christian Ethics states the following (emphasis mine):

This essay's thesis is simple and seemingly quixotic: Affectionate, firm, apprpriate touch is a human need and a moral right. Infants and children require attentive, affetctionate, intimate touch from adults in order to thrive.

Floyd, K. (2015). Affection Exchange Theory. In The International Encyclopedia of Interpersonal Communication (eds C.R. Berger, M.E. Roloff, S.R. Wilson, J.P. Dillard, J. Caughlin and D. Solomon). states (emphasis mine):

Affectionate communication is fundamental to the human relational experience. Across cultures, the expression of affection contributes to the formation, maintenance, and satisfaction level of close personal relationships. Floyd's affection exchange theory (AET) proposes that affectionate communication evolved among humans due to its contributions to the important goals of survival and procreation. This article introduces and evaluates AET, and details empirical work identifying the benefits of affectionate behavior for relationships and individual physical and mental health.

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This suggests that physical intimacy is a necessity for survival. However, I was unable to find any studies that showed that there were clear, observable and repeatable adverse effects on human adults from a lack of physical affection. Are there any studies on that matter?

Answer 1

Short answer: No, science-based sources (including Healthline and Floyd, if you read them carefully) don't claim that physical contact is necessary for survival. Most of the literature on touch deprivation is focused on the benefits of physical affection.

Survival:

While social isolation is often confounded by physical constraints (as in solitary confinement) or mental health factors (as in hikikomori), there are also cases of voluntary isolation with positive outcomes, such as recluses, hermits, and anchorites. Some notable cases of these involve little or no physical contact with others for many years, without apparent adverse effects. There is a selection bias here - this lifestyle is more likely to be adopted by people who prefer less contact - that precludes conclusions about the general public, but it seems safe to say that physical affection is not strictly speaking necessary in adulthood for survival.

The situation in childhood, which is covered better in the other question, is more difficult to test. One example is the case of "bubble boys" such as David Vetter, who spent virtually his entire 12-year life from birth without any direct physical contact with others, though he received much non-physical affection, and appeared to "thrive" as best as can be expected under the circumstances.

Adversity:

Reviews of affection deprivation (eg, Floyd, 2014; Floyd, 2020) mainly focus on the association between perceived lack of physical affection and negative outcomes. As these are mostly correlations, they are not very convincing with respect to causality. Evidence that touch deprivation may have a causal effect on mental and physical health, as reviewed by Ardiel & Rankin (2010) and Field (2010), is largely based on the remedial effects of handling or massage of children with developmental and behavioral issues. However, such studies may also simply indicate that physical affection is an effective treatment, but not necessarily the cause, of underlying issues.

Historically, many children have been raised with high levels of emotional affection but little or no physical affection from their parents - notably in Victorian-era England - and this parenting style does not universally lead to adverse effects in adulthood. For example, some traditional Asian parenting styles are described as "warm" but not physically affectionate, while leading to positive outcomes in adulthood. Lack of controls in such studies preclude firm conclusions, as children may receive physical affection from others (eg, their nursemaids, siblings, or friends) in lieu of their parents. Affectionate parenting styles are recommended for their potential benefits, but evidence for lack of physical affection (independent of emotional affection levels) being responsible for negative outcomes is weak overall.